1. Technical Field
The present invention generally relates to antennas, and more particularly to a microstrip antenna system and method for communicating a dual polarized signal in the microstrip antenna system.
2. Discussion of Related Art
Microstrip antennas have been used for various tasks. Significant development of microstrip antennas began in the early 1970""s. Since then, extensive research and development effort has been expended on exploiting the advantageous features of microstrip antennas which includes, but is not limited to, planar configuration, light weight, low volume, low fabrication costs, and ease of fabrication using standard photolithography techniques.
In a conventional probe-fed antenna system, there are multiple stripline feed circuit layers and each stripline feed circuit layer has a substrate layer above and beneath. A hard-wired feed requires a sequential drill process through the multiple feed circuit layers and the substrate layers, thereby making the fabrication of the probe-fed antenna system complicated and expensive. Additionally, heat can cause thermal-expansion and potentially breakage of the substrate layers comprised in the probe-fed antenna system. The breakage of the substrate layers causes a breakage of the hard-wired feed, thereby resulting in a loss of electrical contact between the probe-fed antenna system and a circuit electrically coupled to the probe-fed antenna system. Moreover, a conventional microstrip configuration, of conventional microstrip antenna systems, is an open structure, thereby allowing radiation in a rearward or backward direction. The microstrip configuration is aperture-coupled. Back radiation is nearly always detrimental to performance of the conventional microstrip antenna systems. The microstrip configuration is also difficult to integrate into additional lower layers of a multi-layered printed circuit.
In a conventional microstrip antenna system by Pozar, as illustrated in Pozar D. M., xe2x80x9cMicrostrip Antenna Aperture-Coupled to a Microstrip-Line,xe2x80x9d Electronics Letters, Vol. 21, 1985, pp. 49-50, there is generally a single slot, which allows only single polarization and not dual polarization of a signal such as an electromagnetic signal. The conventional microstrip antenna system by Pozar is aperture-coupled. Adding a second slot orthogonal to the first slot and centered under a patch antenna, comprised in the microstrip antenna system by Pozar, is generally not possible since two microstrip feed circuits that are located beneath the slots cannot occupy the same space without electrically interfering with each other. Although, it is possible to move the second slot off center of the patch antenna and orthogonal to the first slot, doing so results in poor polarization performance and radiation pattern asymmetry. Hence, the microstrip antenna system by Pozar does not allow dual polarization of the signal. Furthermore, the microstrip antenna system by Pozar is a microstrip configuration, thereby allowing the first slot to radiate the signal in a rearward or backward direction, which is nearly always detrimental to performance of the microstrip antenna system. Additionally, a conventional microstrip antenna system by Zurcher, as illustrated in Zurcher, J. F., P. Gay Balmaz, R. C. Hall, and S. Kolb, xe2x80x9cDual Polarized, Single and Double Layer SSFIP Antennas,xe2x80x9d Microwave and Optics Technology Letters, Vol. 7, 1994, pp. 406-410, comprises a microstrip configuration; thereby resulting in backward radiation that can interfere with signals from electrical systems electrically coupled to the microstrip antenna system.
Thus, a heretofore-unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
The present invention overcomes the inadequacies and deficiencies of the prior art as discussed herein by providing a microstrip antenna system and a method for communicating a dual polarized signal in a microstrip antenna system. An embodiment of the microstrip antenna system includes a stripline feed circuit (SFC) located in an SFC layer. The SFC layer lies between an upper stripline substrate and a lower stripline substrate. A lower ground plane lies below the lower stripline substrate. An upper ground plane lies above the upper stripline substrate.
A preferred embodiment of the microstrip antenna system also comprises an SFC located in an SFC layer. The SFC layer is located between an upper stripline substrate and a lower stripline substrate. A lower ground plane is located below the lower stripline substrate. An upper ground plane is located above the upper stripline substrate. Four slots are located in the upper ground plane. A lower microstrip substrate is located between a lower microstrip patch antenna and the upper ground plane. An upper microstrip substrate is located between an upper microstrip patch antenna and the lower microstrip patch antenna.
A method for communicating a dual polarized signal in the microstrip antenna system comprises the steps of feeding a dual polarized signal from the SFC to the upper stripline substrate, and propagating the dual polarized signal from the upper stripline substrate to the upper ground plane. Another method for communicating a dual polarized signal in the microstrip antenna system comprises the steps of receiving a dual polarized signal from a propagation medium to the upper ground plane, propagating the dual polarized signal from the upper ground plane to the upper stripline substrate and further propagating the dual polarized signal from the upper stripline substrate to the SFC.
Other features and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.